1. Field of the Invention
The present invention relates to an ink jet printhead assembly for use in ink jet printers, and, more particularly, to an ink jet printhead assembly including a nozzle plate with a plurality of ink emitting orifices and a plurality of non-emitting orifices.
2. Description of the Related Art
An ink jet printer typically includes an ink jet printhead assembly having a nozzle plate which is mounted in spaced apart relationship to a printhead. The nozzle plate includes a plurality of ink emitting orifices which are respectively disposed in association with a plurality of heater elements mounted on the printhead. When a particular heater element is actuated or fired, ink disposed adjacent thereto rapidly expands to form a vapor bubble. Ink is expelled through the orifice by the bubble and is jetted onto the print medium.
A problem which sometimes occurs when utilizing a printhead assembly as described above is commonly referred to as "cross-talk." In particular, the nozzle plate is disposed in spaced apart relationship to the printhead, whereby each orifice is disposed in direct fluid communication with an adjacent orifice. The expansion of ink between the nozzle plate and printhead caused by actuating one or more heater elements may, in the worst case, cause jetting of ink from a non-fired orifice. Such "cross-talk" may result in a random sprinkling of ink droplets superimposed onto the printed text, which is obviously not desirable.
One known solution which is used to inhibit cross-talk involves the use of mechanical barrier walls which extend between the nozzle plate and printhead and are disposed between the ink emitting orifices. The barrier walls prevent expanding fluid which occurs upon actuation of a heater element from travelling toward an adjacent orifice.
Another known solution which is used to prevent cross-talk involves the use of a plurality of non-emitting slots which are formed in the nozzle plate. Each non-emitting slot is in the form of an elongated slot associated with a plurality of ink emitting orifices. The nozzle plate is merely disposed in spaced apart relationship to the printhead and no barrier walls or other flow inhibiting structures extend between the nozzle plate and printhead. Each ink emitting orifice is therefore in direct fluid communication with an adjacent ink emitting orifice. The elongated slots are intended to absorb the expansion and contraction of the ink upon firing of a heater element to prevent propagation of fluid surges to adjacent ink emitting orifices, and thereby inhibit cross-talk between the ink emitting orifices.
Another problem with a conventional printhead assembly as described above is that upon firing of a particular heater element, the fluid dynamics within the associated ink emitting orifice are such that a certain minimum time must elapse before the corresponding heater element can be fired again. To wit, when a particular heater element is fired, ink which is in the associated orifice is jetted therefrom onto the print medium, thereby leaving a void or zone of low pressure. The supply of ink between the nozzle plate and printhead rushes into the evacuated ink emitting orifice to fill the same. The inflowing ink momentarily overfills the orifice and then drops back such that the orifice is slightly underfilled. This sets up an oscillation which takes a certain amount of time to settle down. Accordingly, a period of time is required before the heater element can again be actuated, referred to as the "settling time."
The above-mentioned known structures which are utilized for preventing cross-talk between ink emitting orifices are not effective to reduce the settling time of a particular fired heater element and associated ink emitting orifice. Such designs are merely intended to absorb fluid propagation between adjacent ink emitting orifices formed in the nozzle plate.
What is needed in the art is a printhead assembly which reduces the settling time in each ink emitting orifice after ink is jetted therefrom, thereby enabling a faster printing speed.